This is the content of Newton's binomial theorem

What you said upstairs is good.

In fact, you can directly translate it into permutation and combination:

3 1, that is, 3 people choose 1, and the number of selection methods is odd or even.

4 2, that is, 2 out of 4 people are selected, and the method of judging the number of candidates is odd or even.

C(3, 1)=3, odd number. C (4,2) = 6, even number.

C(n, k)%2 == 1 or ==0?

Since k and n are very large, the following formula should be used:

(A/B)% K =(A %(B * K))/B；

(A * B)% K =((A % K)*(B % K))% K；